US6205051B1 - Stabilized magnetic memory cell - Google Patents

Stabilized magnetic memory cell Download PDF

Info

Publication number
US6205051B1
US6205051B1 US09/522,269 US52226900A US6205051B1 US 6205051 B1 US6205051 B1 US 6205051B1 US 52226900 A US52226900 A US 52226900A US 6205051 B1 US6205051 B1 US 6205051B1
Authority
US
United States
Prior art keywords
magnetization
data storage
storage layer
magnetic memory
memory cell
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US09/522,269
Inventor
James A. Brug
Thomas C. Anthony
Manoj K. Bhattarcharyya
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Samsung Electronics Co Ltd
Original Assignee
Hewlett Packard Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hewlett Packard Co filed Critical Hewlett Packard Co
Priority to US09/522,269 priority Critical patent/US6205051B1/en
Application granted granted Critical
Publication of US6205051B1 publication Critical patent/US6205051B1/en
Assigned to SAMSUNG ELECTRONICS CO., LTD. reassignment SAMSUNG ELECTRONICS CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HEWLETT-PACKARD COMPANY
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
    • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
    • G11C11/165—Auxiliary circuits
    • G11C11/1675—Writing or programming circuits or methods

Definitions

  • the present invention pertains to the field of magnetic memories. More particularly, this invention relates to providing a stabilized magnetic memory cell in a magnetic memory.
  • a magnetic memory such as a magnetic random access memory (MRAM) typically includes an array of magnetic memory cells.
  • Each magnetic memory cell usually includes a data storage layer and a reference layer.
  • the data storage layer is usually a layer or film of magnetic material that stores magnetization patterns in orientations that may be altered by the application of external magnetic fields.
  • the reference layer is usually a layer of magnetic material in which the magnetization is fixed or “pinned” in a particular direction.
  • the magnetization pattern in the data storage layer of a magnetic memory cell typically consists of two distinct regions of magnetization—its interior region and its edge regions.
  • the magnetization in the interior region usually aligns with what is commonly referred to as the easy axis of the data storage layer.
  • the magnetization in the edge regions tend to align along the corresponding edges.
  • the overall orientation of magnetization in the data storage layer of a magnetic memory cell results from the magnetization in the interior region as well as the magnetization in the edge regions.
  • the state of a magnetic memory cell depends on the relative orientations of magnetization in its data storage and reference layers.
  • a magnetic memory cell is typically in a low resistance state if the overall orientation of magnetization in its data storage layer is parallel to the orientation of magnetization in its reference layer.
  • a magnetic memory cell is typically in a high resistance state if the overall orientation of magnetization in its data storage layer is anti-parallel to the orientation of magnetization in its reference layer.
  • the logic state of a bit stored in a magnetic memory cell is written by applying external magnetic fields that alter the overall orientation of magnetization in the data storage layer.
  • the external magnetic fields may be referred to as switching fields that switch a magnetic memory cell between its high and low resistance states.
  • a stabilized magnetic memory cell may be defined as one that remains in its high or low resistance state until switched by a well defined switching field.
  • the manufacturing process for a magnetic memory commonly creates surface irregularities near the edges of the data storage layers of individual magnetic memory cells.
  • surface irregularities may be caused by inaccuracies in the patterning steps that form the edges of the data storage layers. This effect usually becomes more pronounced as smaller elements are formed at the limit of lithography used to achieve higher storage densities in a magnetic memory.
  • surface irregularities may render individual magnetic memory cells unstable. For example, such surface irregularities may cause magnetic patterns in the edge regions of a data storage layer which have unpredictable or random orientations and switching behavior.
  • each data storage layer is formed as a rectangle with an elongated dimension along its easy axis.
  • Such a structure usually increases easy axis contribution to the resulting orientation of magnetization in the data storage layer in comparison to contributions from the edges.
  • such a rectangular configuration usually requires more energy to flip the orientation of magnetization in the data storage layer during write operations, thereby causing increase power consumption in an MRAM that uses such a structure.
  • such rectangular magnetic memory cells usually limit the overall memory cell density that may be obtained in an MRAM.
  • a stabilized magnetic memory cell including a data storage layer having an interior region and a pair of end regions near a pair of opposing edges of the data storage layer.
  • the stabilized magnetic memory cell includes a stabilizing material that pins the magnetization in the end regions to a predetermined direction, thereby eliminating randomly oriented patterns of magnetization in the end regions which results in predictable switching behavior of the magnetic memory cell.
  • a method is also disclosed for stabilizing a magnetic memory cell that uses a sequence of write fields to eliminate the randomly oriented patterns of magnetization in the edge regions of the magnetic memory cell.
  • FIGS. 1 a - 1 b illustrate one embodiment of a stabilized magnetic memory cell
  • FIGS. 2 a - 2 b illustrate the orientations of magnetization in the data storage layer for the two stabilized states of the magnetic memory cell
  • FIG. 3 shows a method for stabilizing a magnetic memory cell
  • FIG. 4 is a top view of a magnetic memory which includes an array of magnetic memory cells.
  • FIGS. 1 a - 1 b illustrate one embodiment of a stabilized magnetic memory cell 40 .
  • the magnetic memory cell 40 includes a data storage layer 50 that stores alterable magnetic fields and a reference layer 54 having a pinned orientation of magnetization.
  • the magnetic memory cell 40 further includes layers of stabilizing material 55 - 56 which pin the orientation of magnetization in a pair of end regions 57 - 58 near opposing edges of the data storage layer 50 .
  • the magnetic memory cell 40 includes a tunnel barrier 52 between the data storage layer 50 and the reference layer 54 .
  • This structure of the magnetic memory cell 40 may be referred to as a spin tunneling device in that electrical charge migrates through the tunnel barrier 52 during read operations. This electrical charge migration through the tunnel barrier 52 is due to a phenomenon known as spin tunneling and occurs when a read voltage is applied to the magnetic memory cell 40 .
  • a giant magneto-resistive (GMR) structure may be used in the magnetic memory cell 40 .
  • FIG. 1 a shows a cross-sectional side view of the magnetic memory cell 40 .
  • FIG. 1 b shows a cutaway top view of the magnetic memory cell 40 .
  • the end regions 57 - 58 correspond to a pair of opposing edges of the data storage layer 50 which are perpendicular to the easy axis of the data storage layer 50 .
  • the easy axis of the data storage layer 50 is parallel to an x axis shown.
  • the stabilizing material 55 - 56 pins the orientation of magnetization in the end regions 57 - 58 in a direction which is substantially parallel to a y axis. In an alternative embodiment, the stabilizing material 55 - 56 pins the orientation of magnetization in the end regions 57 - 58 in a direction which is substantially anti-parallel to the y axis.
  • the stabilizing material 55 - 56 not only pins the orientation of magnetization in the end regions 57 - 58 but also provides insulation for the edges of the layers 50 - 54 and prevent electrical coupling to conductors which are used to provide read and write access to the magnetic memory cell 40 .
  • the stabilizing material 55 - 56 is a nickel-oxide material which provides antiferromagnetic properties to pin the end regions 57 - 58 and provides suitable insulating properties.
  • other antiferromagnetic materials such as Fe 2 O 3 or permanent magnet materials may be used for the stabilizing material 55 - 56 .
  • the insulating properties of the stabilizing material 55 - 56 may not be needed so materials such as nickel-manganese are suitable.
  • the stabilizing material 55 - 56 would serve as conductors for adjacent GMR cells as well as pinning materials for edges of individual GMR cells.
  • the dimensions d x and d y are selected to be substantially equal and form a square shape for the data storage layer 50 .
  • the square shape of the data storage layer 50 enhances the density that may be obtained in an MRAM in comparison to that which may be obtained when using rectangular memory cells. This is so because for a given minimum feature size more square magnetic memory cells may be formed on a given substrate area than rectangular magnetic memory cells. In other embodiments, rectangular shapes may be used.
  • the reference layer 54 may be a permalloy layer such as nickel-iron (NiFe) which is coupled to an antiferromagnetic layer that pins the orientation of magnetization in the permalloy layer.
  • the antiferromagnetic material may be iron-manganese (FeMn) or nickel-manganese (NiMn).
  • FeMn iron-manganese
  • NiMn nickel-manganese
  • Alternative materials for the antiferromagnetic material include NiO, TbCo, PtMn, and IrMn.
  • FIGS. 2 a - 2 b illustrate the orientations of magnetization in the data storage layer 50 for the two stabilized states of the magnetic memory cell 40 .
  • FIG. 2 a shows a first stabilized state
  • FIG. 2 b shows a second stabilized state.
  • the magnetization in the interior of the data storage layer 50 rotates about the x axis and the easy axis of the data storage layer 50 in response to applied switching fields.
  • the magnetization in the interior of the data storage layer 50 are oriented substantially anti-parallel to the x axis in the first stabilized state and are oriented substantially parallel to the x axis in the second stabilized state.
  • the magnetic fields in the end regions 57 - 58 are pinned in a direction that is substantially perpendicular to the easy axis of the data storage layer 50 . This prevents one of the first or second stabilized states from being preferred over or more stable than the other.
  • FIG. 3 shows a method for stabilizing the magnetic memory cell 40 .
  • This method uses a bias field to minimize the small regions of randomly oriented patterns of magnetization in the data storage layer 50 before a switching field is applied.
  • the bias field reduces the number of free poles in the side regions of the data storage layer 50 which reduces nucleation sites for undesirable domains.
  • the side regions of the data storage layer 50 are the regions near the opposing edges of the data storage layer 50 which are parallel to the easy axis.
  • the method for stabilizing the magnetic memory cell 40 which includes steps 100 - 106 is set forth for an example in which the orientation of magnetization in the interior of the data storage layer 40 is substantially in the positive x direction and the orientation of magnetization in the end regions 57 - 58 is in the positive y direction.
  • a magnetic field is applied to rotate the magnetization in the end regions 57 - 58 towards a desired direction and to reduce the free poles in the end regions 57 - 58 .
  • the desired direction is in the positive y direction.
  • the magnetic field applied at step 102 is a field in the positive y direction (H y+ ).
  • the reversal of magnetization proceeds by rotation rather than domain nucleation because the magnetization in the side regions of the data storage layer 50 is in the positive x direction at the start of step 102 .
  • the H y+ field affects the end regions 57 - 58 as a bias field to reduce the number of free poles and align the magnetization in the end regions 57 - 58 in the positive y direction.
  • a magnetic field is applied to rotate the orientation of magnetization in the interior of the data storage layer 50 towards a desired logic state.
  • This step writes the magnetic memory cell 40 to its desired first or second logic state of a corresponding bit.
  • the orientation of magnetization is rotated to the negative x direction using a field applied in negative x direction (H x ⁇ ).
  • H x ⁇ a field applied in negative x direction
  • the magnetization in the end regions 57 - 58 and in the side regions of the data storage layer 50 are largely in the positive y direction. Reversal of magnetization is by magnetization rotation rather than domain nucleation.
  • the overall magnetization in the data storage layer after step 104 is closest to the negative x direction and the easy axis.
  • the magnetic field applied at step 102 is removed.
  • the magnetization in the interior region of the data storage layer 50 becomes largely oriented along the x axis.
  • the magnetic field applied at step 104 is removed.
  • the magnetization in the data storage layer 50 remains in the direction that defined the desired logic state, which in the example 10 is the negative x direction.
  • a magnetic field is applied to reduce the free poles in the side regions of the data storage layer 50 .
  • the is direction of the magnetic field is determined by reading the current state of the bit.
  • the field is applied in the same direction as the current state of the bit.
  • the magnetic field applied at step 100 is a field in the positive x direction
  • the method steps 100 - 108 may be employed on the magnetic memory cell 40 whether or not the end regions 57 - 58 are pinned as shown in FIGS. 1 a - 1 b.
  • FIG. 4 is a top view of a magnetic memory 10 which includes an array of magnetic memory cells comprising the magnetic memory cell 40 along with additional magnetic memory cells 41 - 43 .
  • the magnetic memory 10 also includes an array of conductors 20 - 21 and 30 - 31 that enable read and write access to the magnetic memory cells 40 - 43 .
  • the conductors 30 - 31 are top conductors and the conductors 20 - 21 are orthogonal bottom conductors.
  • Each of the magnetic memory cells 40 - 43 has dimensions d x and d y .
  • the magnetic memory cells 40 - 43 are stabilized and their logic states are manipulated by applying electrical currents to the conductors 20 - 21 and 30 - 32 .
  • an electrical current applied to the conductor 30 in the +x direction causes a magnetic field (H y+ ) in the data storage layer 50 in the +y direction according to the right-hand rule.
  • An electrical current applied to the conductor 30 in the ⁇ x direction causes a magnetic field (H y ⁇ ) in the data storage layer 50 in the ⁇ y direction.
  • an electrical current applied to the conductor 20 in the +y direction causes a magnetic field (H x+ ) in the data storage layer 50 in the +x direction
  • an electrical current applied to the conductor 20 in the ⁇ y direction causes a magnetic field (H x ⁇ ) in the data storage layer 50 in the ⁇ x direction.
  • These induced magnetic fields H x+ , H x ⁇ , H y+ , and H y ⁇ may be used to stabilize and/or write the logic state of the magnetic memory cell 40 .

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Hall/Mr Elements (AREA)
  • Mram Or Spin Memory Techniques (AREA)
  • Semiconductor Memories (AREA)

Abstract

A stabilized magnetic memory cell including a data storage layer having an interior region and a pair of end regions near a pair of opposing edges of the data storage layer and a stabilizing material that pins a magnetization in the end regions to a predetermined direction. A method for stabilizing a magnetic memory cell includes the steps of applying a magnetic field that rotates a magnetization in a pair of opposing side regions of a data storage layer of the magnetic memory cell toward a predetermined direction and that reduces free poles in a pair of opposing end regions of the magnetic memory cell, thereby reducing the likelihood of unpredictable switching behavior in the end regions.

Description

CROSS REFERENCE TO RELATED APPLICATION
This is a divisional of application Ser. No. 09/146,819 filed on Sep. 4, 1998 and now issued as U.S. Pat. No. 6,072,717.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention pertains to the field of magnetic memories. More particularly, this invention relates to providing a stabilized magnetic memory cell in a magnetic memory.
2. Art Background
A magnetic memory such as a magnetic random access memory (MRAM) typically includes an array of magnetic memory cells. Each magnetic memory cell usually includes a data storage layer and a reference layer. The data storage layer is usually a layer or film of magnetic material that stores magnetization patterns in orientations that may be altered by the application of external magnetic fields. The reference layer is usually a layer of magnetic material in which the magnetization is fixed or “pinned” in a particular direction.
The magnetization pattern in the data storage layer of a magnetic memory cell typically consists of two distinct regions of magnetization—its interior region and its edge regions. The magnetization in the interior region usually aligns with what is commonly referred to as the easy axis of the data storage layer. The magnetization in the edge regions tend to align along the corresponding edges. The overall orientation of magnetization in the data storage layer of a magnetic memory cell results from the magnetization in the interior region as well as the magnetization in the edge regions.
Typically, the state of a magnetic memory cell depends on the relative orientations of magnetization in its data storage and reference layers. A magnetic memory cell is typically in a low resistance state if the overall orientation of magnetization in its data storage layer is parallel to the orientation of magnetization in its reference layer. In contrast, a magnetic memory cell is typically in a high resistance state if the overall orientation of magnetization in its data storage layer is anti-parallel to the orientation of magnetization in its reference layer.
Typically, the logic state of a bit stored in a magnetic memory cell is written by applying external magnetic fields that alter the overall orientation of magnetization in the data storage layer. The external magnetic fields may be referred to as switching fields that switch a magnetic memory cell between its high and low resistance states. A stabilized magnetic memory cell may be defined as one that remains in its high or low resistance state until switched by a well defined switching field.
The manufacturing process for a magnetic memory commonly creates surface irregularities near the edges of the data storage layers of individual magnetic memory cells. For example, such surface irregularities may be caused by inaccuracies in the patterning steps that form the edges of the data storage layers. This effect usually becomes more pronounced as smaller elements are formed at the limit of lithography used to achieve higher storage densities in a magnetic memory. Unfortunately, such surface irregularities may render individual magnetic memory cells unstable. For example, such surface irregularities may cause magnetic patterns in the edge regions of a data storage layer which have unpredictable or random orientations and switching behavior.
One prior solution for minimizing these negative effects is to form each data storage layer as a rectangle with an elongated dimension along its easy axis. Such a structure usually increases easy axis contribution to the resulting orientation of magnetization in the data storage layer in comparison to contributions from the edges. Unfortunately, such a rectangular configuration usually requires more energy to flip the orientation of magnetization in the data storage layer during write operations, thereby causing increase power consumption in an MRAM that uses such a structure. In addition, such rectangular magnetic memory cells usually limit the overall memory cell density that may be obtained in an MRAM.
SUMMARY OF THE INVENTION
A stabilized magnetic memory cell is disclosed including a data storage layer having an interior region and a pair of end regions near a pair of opposing edges of the data storage layer. The stabilized magnetic memory cell includes a stabilizing material that pins the magnetization in the end regions to a predetermined direction, thereby eliminating randomly oriented patterns of magnetization in the end regions which results in predictable switching behavior of the magnetic memory cell.
A method is also disclosed for stabilizing a magnetic memory cell that uses a sequence of write fields to eliminate the randomly oriented patterns of magnetization in the edge regions of the magnetic memory cell.
Other features and advantages of the present invention will be apparent from the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is described with respect to particular exemplary embodiments thereof and reference is accordingly made to the drawings in which:
FIGS. 1a-1 b illustrate one embodiment of a stabilized magnetic memory cell;
FIGS. 2a-2 b illustrate the orientations of magnetization in the data storage layer for the two stabilized states of the magnetic memory cell;
FIG. 3 shows a method for stabilizing a magnetic memory cell;
FIG. 4 is a top view of a magnetic memory which includes an array of magnetic memory cells.
DETAILED DESCRIPTION
FIGS. 1a-1 b illustrate one embodiment of a stabilized magnetic memory cell 40. The magnetic memory cell 40 includes a data storage layer 50 that stores alterable magnetic fields and a reference layer 54 having a pinned orientation of magnetization. The magnetic memory cell 40 further includes layers of stabilizing material 55-56 which pin the orientation of magnetization in a pair of end regions 57-58 near opposing edges of the data storage layer 50.
In this embodiment, the magnetic memory cell 40 includes a tunnel barrier 52 between the data storage layer 50 and the reference layer 54. This structure of the magnetic memory cell 40 may be referred to as a spin tunneling device in that electrical charge migrates through the tunnel barrier 52 during read operations. This electrical charge migration through the tunnel barrier 52 is due to a phenomenon known as spin tunneling and occurs when a read voltage is applied to the magnetic memory cell 40. In an alternative embodiment, a giant magneto-resistive (GMR) structure may be used in the magnetic memory cell 40.
FIG. 1a shows a cross-sectional side view of the magnetic memory cell 40. FIG. 1b shows a cutaway top view of the magnetic memory cell 40. The end regions 57-58 correspond to a pair of opposing edges of the data storage layer 50 which are perpendicular to the easy axis of the data storage layer 50. The easy axis of the data storage layer 50 is parallel to an x axis shown.
In one embodiment, the stabilizing material 55-56 pins the orientation of magnetization in the end regions 57-58 in a direction which is substantially parallel to a y axis. In an alternative embodiment, the stabilizing material 55-56 pins the orientation of magnetization in the end regions 57-58 in a direction which is substantially anti-parallel to the y axis.
The stabilizing material 55-56 not only pins the orientation of magnetization in the end regions 57-58 but also provides insulation for the edges of the layers 50-54 and prevent electrical coupling to conductors which are used to provide read and write access to the magnetic memory cell 40. In one embodiment, the stabilizing material 55-56 is a nickel-oxide material which provides antiferromagnetic properties to pin the end regions 57-58 and provides suitable insulating properties. In other embodiments, other antiferromagnetic materials such as Fe2O3 or permanent magnet materials may be used for the stabilizing material 55-56.
In embodiments in which the magnetic memory cell 40 is a GMR structure, the insulating properties of the stabilizing material 55-56 may not be needed so materials such as nickel-manganese are suitable. In such embodiments, the stabilizing material 55-56 would serve as conductors for adjacent GMR cells as well as pinning materials for edges of individual GMR cells.
In one embodiment, the dimensions dx and dy are selected to be substantially equal and form a square shape for the data storage layer 50. The square shape of the data storage layer 50 enhances the density that may be obtained in an MRAM in comparison to that which may be obtained when using rectangular memory cells. This is so because for a given minimum feature size more square magnetic memory cells may be formed on a given substrate area than rectangular magnetic memory cells. In other embodiments, rectangular shapes may be used.
The reference layer 54 may be a permalloy layer such as nickel-iron (NiFe) which is coupled to an antiferromagnetic layer that pins the orientation of magnetization in the permalloy layer. The antiferromagnetic material may be iron-manganese (FeMn) or nickel-manganese (NiMn). Alternative materials for the antiferromagnetic material include NiO, TbCo, PtMn, and IrMn.
FIGS. 2a-2 b illustrate the orientations of magnetization in the data storage layer 50 for the two stabilized states of the magnetic memory cell 40. FIG. 2a shows a first stabilized state and FIG. 2b shows a second stabilized state.
The magnetization in the interior of the data storage layer 50 rotates about the x axis and the easy axis of the data storage layer 50 in response to applied switching fields. The magnetization in the interior of the data storage layer 50 are oriented substantially anti-parallel to the x axis in the first stabilized state and are oriented substantially parallel to the x axis in the second stabilized state.
The magnetic fields in the end regions 57-58 are pinned in a direction that is substantially perpendicular to the easy axis of the data storage layer 50. This prevents one of the first or second stabilized states from being preferred over or more stable than the other.
FIG. 3 shows a method for stabilizing the magnetic memory cell 40. This method uses a bias field to minimize the small regions of randomly oriented patterns of magnetization in the data storage layer 50 before a switching field is applied. The bias field reduces the number of free poles in the side regions of the data storage layer 50 which reduces nucleation sites for undesirable domains. The side regions of the data storage layer 50 are the regions near the opposing edges of the data storage layer 50 which are parallel to the easy axis.
The method for stabilizing the magnetic memory cell 40 which includes steps 100-106 is set forth for an example in which the orientation of magnetization in the interior of the data storage layer 40 is substantially in the positive x direction and the orientation of magnetization in the end regions 57-58 is in the positive y direction.
At step 102, a magnetic field is applied to rotate the magnetization in the end regions 57-58 towards a desired direction and to reduce the free poles in the end regions 57-58. In one embodiment, the desired direction is in the positive y direction. In the example, the magnetic field applied at step 102 is a field in the positive y direction (Hy+). The reversal of magnetization proceeds by rotation rather than domain nucleation because the magnetization in the side regions of the data storage layer 50 is in the positive x direction at the start of step 102. The Hy+ field affects the end regions 57-58 as a bias field to reduce the number of free poles and align the magnetization in the end regions 57-58 in the positive y direction.
At step 104, a magnetic field is applied to rotate the orientation of magnetization in the interior of the data storage layer 50 towards a desired logic state. This step writes the magnetic memory cell 40 to its desired first or second logic state of a corresponding bit. In this example, the orientation of magnetization is rotated to the negative x direction using a field applied in negative x direction (Hx−). After step 104, the magnetization in the end regions 57-58 and in the side regions of the data storage layer 50 are largely in the positive y direction. Reversal of magnetization is by magnetization rotation rather than domain nucleation. The overall magnetization in the data storage layer after step 104 is closest to the negative x direction and the easy axis.
At step 106, the magnetic field applied at step 102 is removed. The magnetization in the interior region of the data storage layer 50 becomes largely oriented along the x axis.
At step 108, the magnetic field applied at step 104 is removed. The magnetization in the data storage layer 50 remains in the direction that defined the desired logic state, which in the example 10 is the negative x direction.
In another embodiment, prior to step 102 a magnetic field is applied to reduce the free poles in the side regions of the data storage layer 50. The is direction of the magnetic field is determined by reading the current state of the bit. The field is applied in the same direction as the current state of the bit. In this example, the magnetic field applied at step 100 is a field in the positive x direction The method steps 100-108 may be employed on the magnetic memory cell 40 whether or not the end regions 57-58 are pinned as shown in FIGS. 1a-1 b.
FIG. 4 is a top view of a magnetic memory 10 which includes an array of magnetic memory cells comprising the magnetic memory cell 40 along with additional magnetic memory cells 41-43. The magnetic memory 10 also includes an array of conductors 20-21 and 30-31 that enable read and write access to the magnetic memory cells 40-43. The conductors 30-31 are top conductors and the conductors 20-21 are orthogonal bottom conductors. Each of the magnetic memory cells 40-43 has dimensions dx and dy.
The magnetic memory cells 40-43 are stabilized and their logic states are manipulated by applying electrical currents to the conductors 20-21 and 30-32. For example, an electrical current applied to the conductor 30 in the +x direction causes a magnetic field (Hy+) in the data storage layer 50 in the +y direction according to the right-hand rule. An electrical current applied to the conductor 30 in the −x direction causes a magnetic field (Hy−) in the data storage layer 50 in the −y direction. Similarly, an electrical current applied to the conductor 20 in the +y direction causes a magnetic field (Hx+) in the data storage layer 50 in the +x direction, while an electrical current applied to the conductor 20 in the −y direction causes a magnetic field (Hx−) in the data storage layer 50 in the −x direction. These induced magnetic fields Hx+, Hx−, Hy+, and Hy− may be used to stabilize and/or write the logic state of the magnetic memory cell 40.
The foregoing detailed description of the present invention is provided for the purposes of illustration and is not intended to be exhaustive or to limit the invention to the precise embodiment disclosed. Accordingly, the scope of the present invention is defined by the appended claims.

Claims (10)

What is claimed is:
1. A method for stabilizing a magnetic memory cell, comprising the steps of:
applying a magnetic field that rotates a magnetization in a pair of opposing end regions of a data storage layer of the magnetic memory cell to reduces free poles in the end regions;
applying a magnetic field that rotates an orientation of magnetization in an interior region of the data storage layer to a desired direction for a logic state.
2. The method of claim 1, wherein the desired direction is substantially parallel to an easy axis of the data storage layer.
3. The method of claim 1, wherein the desired direction is substantially anti-parallel to an easy axis of the data storage layer.
4. The method of claim 1, wherein the magnetic field that rotates the magnetization in the opposing end regions is substantially orthogonal to the magnetic field that rotates the orientation of magnetization in the interior region.
5. The method of claim 1, further comprising the step of applying a magnetic field that reduces free poles in a pair of opposing side regions of a data storage layer.
6. The method of claim 1, wherein the step of applying a magnetic field that reduces free poles in a pair of opposing side regions of a data storage layer occurs before the step of applying the magnetic field that rotates a magnetization in the opposing end regions.
7. The method of claim 6, wherein the magnetic field that reduces free poles in the side regions is substantially parallel to the magnetic field that rotates the orientation of magnetization in the interior region.
8. The method of claim 1, further comprising the step of removing the magnetic field that rotates the magnetization in the opposing end regions of the data storage layer.
9. The method of claim 1, further comprising the step of removing the magnetic field that rotates the orientation of magnetization in the interior region of the data storage layer.
10. The method of claim 1, further comprising the step of providing stabilizing material in the magnetic memory cell that pins a magnetization in the end regions to the predetermined direction.
US09/522,269 1998-09-04 2000-03-09 Stabilized magnetic memory cell Expired - Lifetime US6205051B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US09/522,269 US6205051B1 (en) 1998-09-04 2000-03-09 Stabilized magnetic memory cell

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US09/146,819 US6072717A (en) 1998-09-04 1998-09-04 Stabilized magnetic memory cell
US09/522,269 US6205051B1 (en) 1998-09-04 2000-03-09 Stabilized magnetic memory cell

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US09/146,819 Division US6072717A (en) 1998-09-04 1998-09-04 Stabilized magnetic memory cell

Publications (1)

Publication Number Publication Date
US6205051B1 true US6205051B1 (en) 2001-03-20

Family

ID=22519125

Family Applications (2)

Application Number Title Priority Date Filing Date
US09/146,819 Expired - Lifetime US6072717A (en) 1998-09-04 1998-09-04 Stabilized magnetic memory cell
US09/522,269 Expired - Lifetime US6205051B1 (en) 1998-09-04 2000-03-09 Stabilized magnetic memory cell

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US09/146,819 Expired - Lifetime US6072717A (en) 1998-09-04 1998-09-04 Stabilized magnetic memory cell

Country Status (4)

Country Link
US (2) US6072717A (en)
EP (1) EP0986065A3 (en)
JP (1) JP2000100153A (en)
CN (1) CN1186781C (en)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6351409B1 (en) * 2001-01-04 2002-02-26 Motorola, Inc. MRAM write apparatus and method
US6538917B1 (en) * 2001-09-25 2003-03-25 Hewlett-Packard Development Company, L.P. Read methods for magneto-resistive device having soft reference layer
US20030128603A1 (en) * 2001-10-16 2003-07-10 Leonid Savtchenko Method of writing to a scalable magnetoresistance random access memory element
EP1376600A1 (en) * 2002-06-17 2004-01-02 Hewlett-Packard Company Data storage device
US20040027854A1 (en) * 2002-05-15 2004-02-12 Yoshihisa Iwata Magnetic random access memory
US20040264238A1 (en) * 2003-06-27 2004-12-30 Akerman Bengt J. MRAM element and methods for writing the MRAM element
US20050045929A1 (en) * 2003-08-25 2005-03-03 Janesky Jason A. Magnetoresistive random access memory with reduced switching field variation
US20050052902A1 (en) * 2003-09-08 2005-03-10 Smith Kenneth K. Memory device with a thermally assisted write
US20060017083A1 (en) * 2002-07-17 2006-01-26 Slaughter Jon M Multi-state magnetoresistance random access cell with improved memory storage density
US20060108620A1 (en) * 2004-11-24 2006-05-25 Rizzo Nicholas D Reduced power magnetoresistive random access memory elements
US7079414B2 (en) 2003-04-25 2006-07-18 Kabushiki Kaisha Toshiba Magnetic random access memory device
US20070198803A1 (en) * 2006-02-07 2007-08-23 Seagate Technology Llc Storage system with alterable background behaviors
US20100035309A1 (en) * 2008-08-06 2010-02-11 Luca Technologies, Inc. Analysis and enhancement of metabolic pathways for methanogenesis

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6163477A (en) * 1999-08-06 2000-12-19 Hewlett Packard Company MRAM device using magnetic field bias to improve reproducibility of memory cell switching
US20020055190A1 (en) * 2000-01-27 2002-05-09 Anthony Thomas C. Magnetic memory with structures that prevent disruptions to magnetization in sense layer
US6172904B1 (en) * 2000-01-27 2001-01-09 Hewlett-Packard Company Magnetic memory cell with symmetric switching characteristics
US6205053B1 (en) * 2000-06-20 2001-03-20 Hewlett-Packard Company Magnetically stable magnetoresistive memory element
US6236590B1 (en) 2000-07-21 2001-05-22 Hewlett-Packard Company Optimal write conductors layout for improved performance in MRAM
US6538920B2 (en) 2001-04-02 2003-03-25 Manish Sharma Cladded read conductor for a pinned-on-the-fly soft reference layer
US6404674B1 (en) 2001-04-02 2002-06-11 Hewlett Packard Company Intellectual Property Administrator Cladded read-write conductor for a pinned-on-the-fly soft reference layer
US6570783B1 (en) 2001-11-15 2003-05-27 Micron Technology, Inc. Asymmetric MRAM cell and bit design for improving bit yield
JP3769241B2 (en) 2002-03-29 2006-04-19 株式会社東芝 Magnetoresistive element and magnetic memory
US6812538B2 (en) * 2003-02-05 2004-11-02 Applied Spintronics Technology, Inc. MRAM cells having magnetic write lines with a stable magnetic state at the end regions
US6807092B1 (en) * 2003-06-13 2004-10-19 Infineon Technologies Ag MRAM cell having frustrated magnetic reservoirs
US6944053B2 (en) * 2003-06-17 2005-09-13 Hewlett-Packard Development Company, L.P. Magnetic memory with structure providing reduced coercivity
JP4468258B2 (en) 2005-07-15 2010-05-26 株式会社東芝 Magnetoresistive element and magnetic memory
US7999338B2 (en) * 2009-07-13 2011-08-16 Seagate Technology Llc Magnetic stack having reference layers with orthogonal magnetization orientation directions
ITMO20110061A1 (en) * 2011-03-16 2012-09-17 C R D Ct Ricerche Ducati Trent O S R L WHEEL FOR ASSISTED RIDING BICYCLES

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5650958A (en) * 1996-03-18 1997-07-22 International Business Machines Corporation Magnetic tunnel junctions with controlled magnetic response
US5748524A (en) * 1996-09-23 1998-05-05 Motorola, Inc. MRAM with pinned ends
US5756366A (en) * 1995-12-21 1998-05-26 Honeywell Inc. Magnetic hardening of bit edges of magnetoresistive RAM
US5825685A (en) * 1995-11-12 1998-10-20 Oki Electric Industry Co., Ltd. High-speed, low-current magnetoresistive memory device

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3480922A (en) * 1965-05-05 1969-11-25 Ibm Magnetic film device
JPS5033623B1 (en) * 1969-08-16 1975-11-01
JPH0850710A (en) * 1994-04-07 1996-02-20 Read Rite Corp Magnetoresistance effect-type converter with insulating oxide replacement layer
US5946228A (en) * 1998-02-10 1999-08-31 International Business Machines Corporation Limiting magnetic writing fields to a preferred portion of a changeable magnetic region in magnetic devices
US6081445A (en) * 1998-07-27 2000-06-27 Motorola, Inc. Method to write/read MRAM arrays

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5825685A (en) * 1995-11-12 1998-10-20 Oki Electric Industry Co., Ltd. High-speed, low-current magnetoresistive memory device
US5756366A (en) * 1995-12-21 1998-05-26 Honeywell Inc. Magnetic hardening of bit edges of magnetoresistive RAM
US5650958A (en) * 1996-03-18 1997-07-22 International Business Machines Corporation Magnetic tunnel junctions with controlled magnetic response
US5748524A (en) * 1996-09-23 1998-05-05 Motorola, Inc. MRAM with pinned ends

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6351409B1 (en) * 2001-01-04 2002-02-26 Motorola, Inc. MRAM write apparatus and method
US6538917B1 (en) * 2001-09-25 2003-03-25 Hewlett-Packard Development Company, L.P. Read methods for magneto-resistive device having soft reference layer
US20030128603A1 (en) * 2001-10-16 2003-07-10 Leonid Savtchenko Method of writing to a scalable magnetoresistance random access memory element
US7209382B2 (en) 2002-05-15 2007-04-24 Kabushiki Kaisha Toshiba Magnetic random access memory
US20040027854A1 (en) * 2002-05-15 2004-02-12 Yoshihisa Iwata Magnetic random access memory
US7050325B2 (en) 2002-05-15 2006-05-23 Kabushiki Kaisha Toshiba Magnetic random access memory
US20060092692A1 (en) * 2002-05-15 2006-05-04 Yoshihisa Iwata Magnetic random access memory
US6905888B2 (en) 2002-06-17 2005-06-14 Hewlett-Packard Development Company, L.P. Magnetic memory element having controlled nucleation site in data layer
EP1376600A1 (en) * 2002-06-17 2004-01-02 Hewlett-Packard Company Data storage device
KR100972631B1 (en) * 2002-06-17 2010-07-28 삼성전자주식회사 Magnetic memory element having controlled nucleation site in data layer
CN100442384C (en) * 2002-06-17 2008-12-10 三星电子株式会社 Magnetic memory element for controlling nucleation position in data layer
US20040062125A1 (en) * 2002-06-17 2004-04-01 Nickel Janice H. Magnetic memory element having controlled nucleation site in data layer
US6803616B2 (en) 2002-06-17 2004-10-12 Hewlett-Packard Development Company, L.P. Magnetic memory element having controlled nucleation site in data layer
US20060017083A1 (en) * 2002-07-17 2006-01-26 Slaughter Jon M Multi-state magnetoresistance random access cell with improved memory storage density
US7079414B2 (en) 2003-04-25 2006-07-18 Kabushiki Kaisha Toshiba Magnetic random access memory device
US20040264238A1 (en) * 2003-06-27 2004-12-30 Akerman Bengt J. MRAM element and methods for writing the MRAM element
US20050045929A1 (en) * 2003-08-25 2005-03-03 Janesky Jason A. Magnetoresistive random access memory with reduced switching field variation
US6961263B2 (en) 2003-09-08 2005-11-01 Hewlett-Packard Development Company, L.P. Memory device with a thermally assisted write
US20050052902A1 (en) * 2003-09-08 2005-03-10 Smith Kenneth K. Memory device with a thermally assisted write
US20060108620A1 (en) * 2004-11-24 2006-05-25 Rizzo Nicholas D Reduced power magnetoresistive random access memory elements
US20070198803A1 (en) * 2006-02-07 2007-08-23 Seagate Technology Llc Storage system with alterable background behaviors
US8200869B2 (en) 2006-02-07 2012-06-12 Seagate Technology Llc Storage system with alterable background behaviors
US20100035309A1 (en) * 2008-08-06 2010-02-11 Luca Technologies, Inc. Analysis and enhancement of metabolic pathways for methanogenesis

Also Published As

Publication number Publication date
CN1186781C (en) 2005-01-26
CN1247367A (en) 2000-03-15
EP0986065A3 (en) 2000-12-27
US6072717A (en) 2000-06-06
EP0986065A2 (en) 2000-03-15
JP2000100153A (en) 2000-04-07

Similar Documents

Publication Publication Date Title
US6205051B1 (en) Stabilized magnetic memory cell
US5982660A (en) Magnetic memory cell with off-axis reference layer orientation for improved response
US6654278B1 (en) Magnetoresistance random access memory
US7235408B2 (en) Synthetic antiferromagnetic structure for magnetoelectronic devices
EP1126469B1 (en) Magnetic memory
US6358757B2 (en) Method for forming magnetic memory with structures that prevent disruptions to magnetization in sense layers
KR100893852B1 (en) Multi-bit magnetic memory cells
US6205053B1 (en) Magnetically stable magnetoresistive memory element
US6134139A (en) Magnetic memory structure with improved half-select margin
US6081446A (en) Multiple bit magnetic memory cell
US6479353B2 (en) Reference layer structure in a magnetic storage cell
KR100752068B1 (en) Magnetic random access memory designs with patterned and stabilized magnetic shields
EP1248265A2 (en) Magnetic memory cell
US20050237793A1 (en) Magnetic random access memory designs with controlled magnetic switching mechanism by magnetostatic coupling
KR20040058244A (en) Writing to a scalable MRAM element
US6661688B2 (en) Method and article for concentrating fields at sense layers
US6906947B2 (en) In-plane toroidal memory cell with vertically stepped conductors
WO2002005318A2 (en) High density giant magnetoresistive memory cell
JP4900647B2 (en) Magnetic random access memory
KR100915975B1 (en) Method for switching magnetic moment in magnetoresistive random access memory with low current

Legal Events

Date Code Title Description
STCF Information on status: patent grant

Free format text: PATENTED CASE

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 4

AS Assignment

Owner name: SAMSUNG ELECTRONICS CO., LTD., KOREA, REPUBLIC OF

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HEWLETT-PACKARD COMPANY;REEL/FRAME:019725/0320

Effective date: 20070518

FPAY Fee payment

Year of fee payment: 8

FPAY Fee payment

Year of fee payment: 12